CDX-011, which suppresses GPNMB protein levels, is not effective for slowing tumor progression in patients with previously treated osteosarcoma, according to an oral presentation at the Connective Tissue Oncology Society (CTOS) 2017 Annual Meeting.1

Patients with recurrent or refractory osteosarcoma have few treatment options and face a poor prognosis. Osteosarcoma cells express high levels of GPNMB, representing a potential therapeutic target.

For this single-arm phase 2 study, researchers enrolled 22 patients with recurrent or refractory osteosarcoma to receive CDX-011, which was previously shown to indirectly inhibit GPNMB. Immunohistochemistry was used to determine GPNMB expression.

At the time of analysis, immunohistochemistry data from 4 patients were missing, 1 patient's efficacy data could not yet be evaluated, and 3 patients' data were excluded from the efficacy analysis because of stratification for prior eribulin therapy.

Of the 19 patients included in the efficacy analysis, only 1 partial response was recorded and 2 patients had stable disease. No significant association between GPNBM levels and disease response was found. Due to futility, the researchers did not pursue a second stage of the trial.

The most common grade 3 adverse event was rash. One patient died from multiple toxicities, though the authors noted that these toxicities “were determined to not be solely related to CDX-011.”

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